Bounce Types


BounceStudio API sorts your bounced email messages into the following categories. In the table below, the "Bounce Type" column contains the return code value returned by the bsBounceCheck() function.

Bounce TypeDescription
0NON BOUNCE
10HARD BOUNCE
20SOFT BOUNCE - General
21SOFT BOUNCE - Dns Failure
22SOFT BOUNCE - Mailbox Full
23SOFT BOUNCE - Message Size Too Large
30BOUNCE WITH NO EMAIL ADDRESS
40GENERAL BOUNCE
50MAIL BLOCK - General
51MAIL BLOCK - Known Spammer
52MAIL BLOCK - Spam Detected
53MAIL BLOCK - Attachment Detected
54MAIL BLOCK - Relay Denied
60AUTO REPLY
70TRANSIENT BOUNCE
80SUBSCRIBE REQUEST
90UNSUBSCRIBE REQUEST
100CHALLENGE RESPONSE





Auto Reply (AR):  An automatic response from the recipient.
Examples: "Out Of Office", "Vacation Message"


Bounce With No Email Address (BN):  BounceStudio API determined that the message was a bounce, but it could not resolve the original email recipient email address. Rare.



Challenge-Response Message (CR):   Challenge-Response email systems were created as a reaction to the increasing circulation of spam. Dubbed as a 100% effective solution to stopping spam from ever reaching users' inboxes, Challenge-Response systems like EarthLink SpamBlocker and SpamArrest, among others, require human intervention for an email message to reach its intended recipient.

In short, a Challenge-Response message is an automatic response from the recipient, requesting that the sender confirm a real person is sending the message. Generally, confirmation is completed manually by clicking on a hyperlink within the Challenge-Response message itself.

When BounceStudio API determines a message is a Challenge-Response type message, the email address that is returned is the FROM: email address of the system, or person, sending the Challenge-Response message to you. It's been our experience that the original email address of the recipient does not appear within the Challenge-Response message, thus there is no way to retrieve the original email address. You'll be handling these types of messages manually, because that's what they're designed for, so it should be okay that the original email address isn't returned.



General Bounce (GB):  The email server could not deliver your email message, but the bounce message was unclear as to what kind of bounce it was. Most BounceStudio API users treat these as soft bounces.
Example: "Subject: Undeliverable mail"


Hard Bounce (HB):  The email server could not deliver your email message.
Example: "550 User Unknown"


Mail Block - General (MB):  Indicates that the recipient's email server is blocking email from your email server.
Example: "550 Message REFUSED by peer"


Mail Block - Known Spammer (MBKS):  Indicates that the recipient's email server is blocking email from your email server because it believes you are a known spammer.
Example: "REJECT Known SPAM source"


Mail Block - Spam Detected (MBSD):  Indicates that the recipient's email server is blocking email from your email server because the message appears to have content that looks like spam.
Example: "550 Possible spam detected"


Mail Block - Attachment Detected (MBAD):  Indicates that the recipient's email server is blocking email from your email server because the email message contained an attachment.
Example: "552 Disapproved attachment"


Mail Block - Relay Denied (MBRD):  Indicates that the recipient's email server is blocking email from your email server.
Example: "551 relaying denied"


Non Bounce (NB):  BounceStudio API determined that the message was not a bounce. This could be a recipient reply, or maybe a bounce format that BounceStudio API did not recognize.



Soft Bounce - General (SB):  The email server is temporarily unable to deliver your message to the recipient email address.
Example: "Connection timed out."


Soft Bounce - Dns Failure (SBDF):  The email server is temporarily unable to deliver your message to the recipient email address because of a DNS problem.
Example: "Host is unreachable"


Soft Bounce - Mailbox Full (SBMF):  The email server is temporarily unable to deliver your message to the recipient email address because the recipient's email box is full.
Example: "Mailbox over quota"


Soft Bounce - Message Size Too Large (SBMS):  The email server could not deliver your message to the recipient because the message size is too large.
Example: "Exceeded maximum inbound message size"


Subscribe Request (SR):  Someone is requesting to be added to your opt-in email list. BounceStudio API looks for subscribe requests in the subject header of the email message, and on the first line of a text based email message. BounceStudio API parses for subscribe requests in several different 7-bit ascii langauges. (ie. English, Spanish, French, German, etc.)



Transient Bounce (TB):  The email server temporarily can not deliver your message, but it is still trying.
Examples: "Warning: message still undelivered after 4 hours. Will keep trying until message is 2 days old"


Unsubscribe Request (UR):  Recipient is requesting to be removed from future email from you. BounceStudio API looks for unsubscribe/remove requests in the subject header of the email message, and on the first line of a text based email message. BounceStudio API parses for unsubscribe requests in several different 7-bit ascii langauges. (ie. English, Spanish, French, German, etc.)